Method and apparatus for a hybrid variable rate pipe

ABSTRACT

A method and apparatus for a hybrid variable rate pipe is described. In one embodiment of the invention, a computer implemented method comprises provisioning a hybrid variable rate pipe on a span of an optical ring and transmitting a set of traffic in the hybrid variable rate pipe.

CROSS-REFERENCE TO RELATED APPLICATIONS

This is a continuation of U.S. Provisional Patent Application Number60/258,759, entitled “Method and Apparatus For A Hybrid Variable RatePipe” filed on Dec. 30, 2000.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to communication networks. More specifically, thepresent invention relates to communication over optical networks.

2. Description of the Related Art

Current networks must satisfy consumer demand for more bandwidth and aconvergence of voice and data traffic. The increased demand of bandwidthby consumers combines with improved high bandwidth capacity of corenetworks to make edge networks a bottleneck despite the capacity ofoptical networks.

Multiplexing is used to deliver a variety of traffic over a single highspeed broadband line. An optical standard such as Synchronous OpticalNetwork (SONET) or Synchronous Digital Hierarchy (SDH) in conjunctionwith a multiplexing scheme is used to deliver various rates of trafficover a single high speed optical fiber. SONET/SDH is a transmissionstandard for optical networks which corresponds to the physical layer ofthe open standards institutes (OSI) network model. One of the protectionschemes for SONET/SDH involves automatic protection switching (APS) in abi-directional line switched ring (BLSR) architecture. BLSR utilizeslinear switching to implement APS.

FIGS. 1 a-1 e are diagrams illustrating an example of traffic flow in aBi-Directional Line Switched Ring (BLSR) while there is and is not afailure in the ring. FIG. 1 a (Prior Art) is a diagram of exemplarytraffic flow on a BLSR while there is not a failure. Although a BLSR hasa working channel and a protection channel for traffic flowing East andWest, only one working channel and its protection channel (whichtraverse the ring in the opposite direction) are shown in FIGS. 1 a and1 b. In FIG. 1 a, a stream of traffic 113 is received from a sourceexternal to the ring at node 101. Node 101 transmits this traffic 113over its East span 115 on a working channel 119 to a node 103. Node 103transmits the traffic 113 over its East span 117 in a working channel121 to node 105. The stream of TDM traffic 113 exits the ring at node105 to a destination external to the ring. Although extra traffic may beflowing in the protection channels of the ring, only the stream of TDMtraffic 113 is shown for simplicity.

FIG. 1 b (Prior Art) is a diagram of exemplary traffic flow on the BLSRwhile there is a failure. In FIG. 1 b, the node 103's East span 117 hasfailed (e.g. severed lines). The stream of TDM traffic 113 is protectionswitched at node 103. Node 103 informs the other nodes in the ring ofthe failure. The stream of TDM traffic 113 is transmitted back to node101 from node 103 in the protection channel 110 of node 103's West span115. The stream of TDM traffic 113 continues around the ring to node 105along a protection path. The protection path includes the protectionchannels 114, 120, 128, and 120 carrying traffic between nodes 101 and107, 107 and 109, 109 and 111, and 111 and 105 respectively.

FIG. 1 c (Prior Art) is a diagram of exemplary traffic flow on the BLSRwhile there is not a failure. In FIG. 1 c, transmit working andprotection channels 137, 110 and receiving working and protectionchannels 119, 139 of node 103's West span 115 are shown. Similarly,transmit working and protection channels 121, 135 and receiving workingand protection channels 141, 143 of node 103's East span 117 are shown.The transmit working channel 137 and the receiving protection channel139 of node 103's West span 115 are not shown in FIGS. 1 a and 1 b forsimplicity. The transmit protection channel 135 and the receivingworking channel 141 of node 103's East span 117 are also not shown inFIGS 1 a and 1 b for simplicity. A stream of working TDM traffic 104 istransmitted in the transmit working channel 137 from node 103 to node101. Another stream of working TDM traffic 113 is received in thereceiving working channel 119 and transmitted to node 105 in thetransmit working channel 121 while there is not a failure. The receiveworking channel 141 carries TDM traffic not shown in the figure.

FIG. 1 d (Prior Art) is a diagram of exemplary traffic flow on the BLSRwhile there is a failure. In FIG. 1 d, the stream of working TDM traffic104 continues to be transmitted in the transmit working channel 137. Thestream of TDM traffic 113 is protection switched to the transmitprotection channel 110 while there is a failure.

The ring described in FIGS 1 a-1 d can be a 2 fiber or 4 fiber BLSR. Thechannels described in FIGS. 1 a-1 d are logical channels which mayreside on different optical fibers depending on the ring architecture. Aring switch, which is a protection switch that occurs in both 2 fiberand 4 fiber BLSRs, is illustrated in FIGS. 1 c-1 d.

FIG. 1 e (Prior Art) is a diagram illustrating a span switch for a 4fiber BLSR while the transmit working channel 121 of FIGS. 1 c-1 dfails. In FIGS. 1 e, the transmit working channel 121 of node 103 fails.In a 4 fiber optical ring, the failure is detected and the stream of TDMtraffic 113 is span switched to the transmit protection channel 135. Aspan switch is a protection switch which occurs in a 4 fiber BLSR.Physically, the East span 117 is 2 fibers. The transmit working channel121 exists on one fiber and the transmit protection channel 135 existson a separate fiber. The failure of the working channel 121 is a failureof the first fiber. In this example, the two fibers 121 and 133 are inseparate conduits. Since the fibers run in separate conduits, a failurecaused by severing will not affect both fibers. The stream of TDMtraffic 113 is switched from being transmitted over the first fiber tobeing transmitted over the second fiber.

High speed optical rings offer large amounts of bandwidth, but theprotection scheme utilizes at most 50% of that bandwidth. This 50% ofmaximum possible total bandwidth for a protection channel often goesunused while there is not a failure. It is often unused because traffictransmitted in the protection channel would be preempted by the workingTDM traffic while a failure occurs.

FIGS. 2 a and 2 b are diagrams illustrating the use of a protectionchannel to carry extra time division multiplexed (TDM) traffic whilethere is and is not a failure . FIG. 2 a (Prior Art) is a diagramillustrating the use of a protection channel to carry extra TDM trafficwhile there is not a failure. In FIG. 2 a, a West span 201 is dividedinto a working channel 205 and a protection channel 207. The workingchannel 205 carries TDM traffic 209 and the protection channel 207carries extra TDM traffic 211. An East span 203 is also divided into aworking channel 204 and a protection channel 206. The working channel204 of the East span 203 carries TI)M traffic 213 and the protectionchannel 206 carries extra TDM traffic 215.

FIG. 2 b (Prior Art) illustrates preemption of extra TDM traffic whilethere is a failure. In FIG. 2 b, the East span 203 has failed. Theworking TDM traffic 213 is protection switched into the protectionchannel 207 of the West span 201. The protection switched working TDMtraffic 213 preempts the extra TDM traffic 211 which was previouslycarried in the protection channel 207 of the West span 201. The extraTDM traffic 215 previously transmitted over the protection channel 207of the East span 203 is not protected and is therefore completely lostupon the failure. The extra TDM traffic is problematic to sell tocustomers because it is preemptable and unprotected. A consumer couldpurchase the extra traffic service from two network owners or providersand alternate between the two upon failures. While the above is true fora 2 fiber BLSR, the impact to extra TDM traffic in a 4 fiber BLSRdepends on the type of failure. In particular, while a ring switch in 4fiber BLSR operates in a similar manner as described above, a spanswitch in a 4 fiber BLSR does not impact the extra TDM traffictransmitted on the non-failing spans.

An alternative to unprotected preemptable traffic in a protectionchannel is to provide a non-preemptable unprotected traffic (NUT)channel. A NUT channel allows for an implementation that runs aunidirectional path switched ring (UPSR) over a BLSR. Other examplesinclude ATM 1+1 protection schemes which can traverse over the NUTchannel. Thus, a NUT channel is used to provide two circuit levelprotection schemes.

SUMMARY OF THE INVENTION

The invention provides a method and apparatus for provisioning anon-BLSR protected layer 2/3 channel. According to one aspect of theinvention, a computer implemented method provides for provisioning ahybrid variable rate pipe on a span of an optical ring and transmittinga set of traffic in the hybrid variable rate pipe.

These and other aspects of the present invention will be betterdescribed with reference to the Detailed Description.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention may best be understood by referring to the followingdescription and accompanying drawings that are used to illustrateembodiments of the invention. In the drawings:

FIG. 1 a (Prior Art) is a diagram of exemplary traffic flow on a BLSRwhile there is not a failure.

FIG. 1 b (Prior Art) is a diagram of exemplary traffic flow on the BLSRwhile there is a failure.

FIG. 1 c (Prior Art) is a diagram of exemplary traffic flow on the BLSRwhile there is not a failure.

FIG. 1 d (Prior Art) is a diagram of exemplary traffic flow on the BLSRwhile there is a failure.

FIG. 1 e (Prior Art) is a diagram illustrating a span switch for a 4fiber BLSR while the transmit working channel 121 of FIGS. 1 c-1 dfails.

FIG. 2 a (Prior Art) is a diagram illustrating the use of a protectionchannel to carry extra TDM traffic while there is not a failure.

FIG. 2 b (Prior Art) illustrates preemption of extra TDM traffic whilethere is a failure.

FIG. 3 a is a conceptual diagram of the bandwidth of an optical ringdivided into channels according to one embodiment of the invention.

FIG. 3 b is a diagram illustrating traffic flow with a non-BLSRprotected Layer 2/3 channel of the East and West transmit fibers 313 and319 of FIG. 3 a whenever there is no failure on the ring according toone embodiment of the invention.

FIG. 3 c is a diagram illustrating an example of traffic flow whilethere is a failure in the ring according to one embodiment of theinvention.

FIG. 3 d is a diagram of exemplary traffic flow whenever there is and isnot a failure in the six node ring illustrated in FIG. 3 a having anon-BLSR protected layer 2/3 channel and carrying extra TDM trafficaccording to one embodiment of the invention.

FIG. 3 e is a diagram of exemplary traffic flow while there is and isnot a failure in the six node ring illustrated in FIG. 3 a wherein anon-BLSR protected Layer 2/3 channel is protected using Layer 2/3 BLSRprotection according to one embodiment of the invention.

FIG. 4 a is a conceptual diagram illustrating the allocation ofbandwidth of an optical fiber according to one embodiment of theinvention

FIG. 4 b is a conceptual diagram of the division of bandwidth accordingto a paired channel protection scheme in on an optical fiber accordingto one embodiment of the invention.

FIG. 4 c is a conceptual diagram illustrating the allocation ofbandwidth of the fiber in accordance with an inverted channel protectionscheme according to one embodiment of the invention.

FIG. 5 is a flowchart for providing an alternative path for protectingnon-BLSR protected Layer 2/3 TDM traffic in BLSR protection time usingLayer 2/3 BLSR protection according to one embodiment of the invention.

FIG. 6 is a conceptual diagram illustrating an exemplary division of anoptical span's bandwidth according to one embodiment of the invention.

FIG. 7 a is a diagram illustrating an example traffic flow while thereis not a failure in an optical span according to one embodiment of theinvention.

FIG. 7 b is a diagram illustrating an example traffic flow while thereis a failure in an optical span according to one embodiment of theinvention.

FIG. 7 c is a diagram of the example traffic flow 719 of FIGS. 7 a and 7b while there is not and is a failure of the span 703 of FIGS. 7 a and 7b in a ring according to one embodiment of the invention.

FIG. 8 is a flowchart for allocating a layer 2/3 pipe and subpipes in anoptical ring according to one embodiment of the invention.

FIG. 9 a is a conceptual diagram illustrating exemplary traffic flowover an optical ring having a variable rate layer 2/3 pipe and anon-BLSR protected layer 2/3 channel while there is not a failureaccording to one embodiment of the invention.

FIG. 9 b is a diagram illustrating exemplary traffic flow over a opticalring having the variable rate layer 2/3 pipe and the non-BLSR protectedlayer 2/3 channel during a failure in the ring according to oneembodiment of the invention.

FIG. 10 is a diagram of circuit components in a hybrid network elementaccording to one embodiment of the invention.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth toprovide a thorough understanding of the invention. However, it isunderstood that the invention may be practiced without these specificdetails. In other instances, well-known protocols, circuits, structuresand techniques have not been shown in detail in order not to obscure theinvention.

According to one embodiment of the invention, one or more non-BLSRprotected channels is added to a ring to carry Layer 2/3 TDM traffic(referred to herein as a non-BLSR protected Layer 2/3 channel). The termchannel is used herein in a context specific manner. For instance, theterm channel is used herein to refer to a physical channel on a fiber.However, the use of the term channel is also used to refer to the higherlevel constructs of a non-BLSR protected Layer 2/3 channel, a workingchannel, and a protection channel, which can each refer to groupings ofone or more physical channels on a fiber. In this ring network, networkelements are used that can transmit and receive TDM ring traffic. Inaddition, at least certain of the network elements (referred to hereinas hybrid network elements) provide two different switchingtechniques—TDM and packet. The packet switching provided can support anynumber of protocols including layer 2 and layer 3 type protocols such asATM, Ethernet, Frame Relay, IP, etc. In addition to typical operationsof a TDM network element, the hybrid network elements are implemented tobe able to: 1) programmably select on an STS basis certain, of theincoming TDM traffic to be extracted and packet switched rather than TDMswitched; and/or 2) receive packet traffic in another form to be packetswitched. Regardless of which switching technique is used, the switchedtraffic going back onto the ring is put in TDM format and transmittedout. However, each time traffic is packet switched, that traffic can bestatistically multiplexed. An exemplary implementation of such hybridnetwork elements is provided herein with reference to FIG. 10.

The term Layer 2/3 TDM traffic is used herein to refer to traffic thatis in some packet based form (e.g., Ethernet, IP, ATM, IP, etc) that: 1)can be extracted from the Layer 1 TDM format used to carry the Layer 2/3TDM traffic on the spans; and 2) can be switched on a packet basis bythe hybrid network elements described above.

The non-BLSR protected Layer 2/3 channel is configured to be the samewidth around the entire ring. While it is not necessary, in oneembodiment a single non-BLSR protected Layer 2/3 channel is configuredon a given ring. In addition, while it is not necessary, in oneembodiment, the traffic to be carried on the non-BLSR protected layer2/3 channel must enter and be terminated through a packet switch of ahybrid network element to allow for compatibility with existing BLSRnetwork elements as described later herein.

FIGS. 3 a-3 d illustrate traffic flow in response to a failure in a ringwith a non-BLSR protected Layer 2/3 channel according to one embodimentof the invention. FIG. 3 a is a conceptual diagram of the bandwidth ofan optical ring divided into channels according to one embodiment of theinvention. The optical ring illustrated in FIG. 3 a is a six node BLSR.Each node 301, 303, 305, 307, 309, and 311 in the ring has an East andWest span. Each span includes a transmit fiber and a receive fiber. Fromnode 301's perspective, 313 is its East transmit fiber. The bandwidthfor each fiber is divided into three channels: a working channel 321, aprotection channel 327, and a non-BLSR protected Layer 2/3 channel 323.The protection channel 327 is to protect the working channel 321 of301's West transmit fiber 319. Similarly, the West transmit fiber's 319protection channel 327 protects the working channel 321 of node 301'sEast transmit fiber 313. According to one exemplary use, TDM traffic istransmitted over the working channel 321, while Layer 2/3 TDM traffic(e.g. cells, packets, etc.) is transmitted over the non-BLSR protectedLayer 2/3 channel 323.

FIG. 3 b is a diagram illustrating traffic flow with a non-BLSRprotected Layer 2/3 channel of the East and West transmit fibers 313 and319 of FIG. 3 a whenever there is no failure on the ring according toone embodiment of the invention. TDM traffic 325 is being transmittedover the working channel 321 of the West transmit fiber 319. Non-BLSRprotected Layer 2/3 TDM traffic 329 is being transmitted over thenon-BLSR protected Layer 2/3 channel 323 of the West transmit fiber 319.In this illustration, the protection channel 327 of the West transmitfiber 319 is idle, but extra TDM traffic can be carried over theprotection channel 327. East flowing TDM traffic 333 is transmitted overthe working channel 321 of the East transmit fiber 313. Non-BLSRprotected Layer 2/3 TDM traffic 335 is being transmitted over thenon-BLSR protected layer 2/3 channel 323 of the East transmit fiber 313.In this example, the protection channel 327 of the East transmit fiber313 is idle, but the protection channel of the East transmit fiber 313can carry extra TDM traffic.

FIG. 3 c is a diagram illustrating an example of traffic flow whilethere is a failure in the ring according to one embodiment of theinvention. In this example, the East transmit fiber 313 has failed(e.g., broken line). The West transmit fiber 319 now carries three flowsof traffic. The previously East flowing TDM traffic 333 is protectionswitched to the protection channel 327 of the West transmit fiber 319.The working channel 321 of the West transmit fiber 319 continues tocarry the West flowing TDM traffic 325. The non-BLSR protected Layer 2/3channel 323 continues to carry the West flowing non-BLSR protected Layer2/3 TDM traffic 329. The protection channel 327 of the West transmitfiber 319 is no longer idle and now carries the previously East flowingTDM traffic 333. If the protection channel 327 of the West transmitfiber 319 carried extra TDM traffic, that extra TDM traffic is droppedover the entire ring. Also note that because the non-BLSR protectedlayer 2/3 TDM traffic 335 is not protected by BLSR, it will be droppedand/or protected by another higher level mechanism as described laterherein.

FIG. 3 d is a diagram of exemplary traffic flow whenever there is and isnot a failure in the six node ring illustrated in FIG. 3 a having anon-BLSR protected layer 2/3 channel and carrying extra TDM trafficaccording to one embodiment of the invention. In FIG. 3 d, TDM traffic351 and extra TDM traffic 355 enter the BLSR through node 301. TDMtraffic 351 is transmitted to node 303 over the working channel 321 ofnode 301's East transmit fiber 313. The extra TDM traffic 355 istransmitted from node 301 to node 307 on the protection channel 327 ofnode 301's West transmit fiber 319. Two flows of Layer 2/3 TDM traffic353, 357 also enter the BLSR through node 301. In one embodiment, layer2/3 TDM traffic must be switched through a packet mesh when entering andexiting the ring. Layer 2/3 TDM traffic 353 is transmitted over thenon-BLSR protected channel 323 of node 301's East transmit fiber 313 tonode 303 where it exits the ring. Layer 2/3 TDM traffic 357 istransmitted over the non-BLSR protected layer 2/3 channel 323 of node301's West transmit fiber 319 to node 307. The layer 2/3 traffic 353,357 does not necessarily come from the same input port on a line card.The traffic 353, 357 can arrive on any port on any line card in node 301as long as some switching mechanism (e.g., packet switching, frameswitching, etc.) directs the incoming layer 2/3 traffic to the East orWest bound channel 323.

If the East transmit fiber 313 fails, the TDM traffic 351 is protectionswitched to the protection channel 327 of node 301's West transmit fiber319. Any traffic being transmitted over the counter-clockwise protectionpath of the ring, including the extra TDM traffic 355 is preempted bythe TDM traffic 351. In contrast, only the layer 2/3 TDM traffic 353 isdropped from the perspective of typical BLSR protection (otherprotection may be provided as described later herein). The othernon-BLSR protected layer 2/3 channels are unaffected by the spanfailure. Hence, the layer 2/3 TDM traffic 357 is unaffected by thefailure of node 301's East transmit fiber 313.

Since a segment of the bandwidth of a ring is allocated to a non-BLSRprotected layer 2/3 channel, more of the ring bandwidth can be utilizedafter a span failure in the ring. Typically, a failure results in losingOC-n of ring traffic (if the ring is carrying extra TDM traffic), wheren is half the ring's total bandwidth. The amount of bandwidth lost dueto a failure decreases in proportion to the amount of bandwidthallocated to a non-BLSR protected layer 2/3 channel.

The addition of the non-BLSR protected Layer 2/3 channel enables aprovider to deliver up to three types of services. Firstly, the providercan provide typical guaranteed service for TDM traffic. Secondly, theprovider can provide the protection channel to carry preemptable extraTDM traffic. Thirdly, the provider can provide the non-BLSR protectedLayer 2/3 channel to carry Layer 2/3 TDM traffic. It should be notedthat the second service is not provided without the first, but that thefirst and third are independent and either could be the only serviceexisting on the ring at a given time. Thus, according to one aspect ofthe invention, a ring architecture is described that can be operated asa BLSR ring for TDM traffic (e.g., telecom traffic), a set of routers(e.g., for data traffic), or both. The hybrid network elements on thering can therefore be viewed as part of a TDM ring, a packet network, orboth (e.g., a typical IP router can interact with one of the hybridnetwork elements as a TDM network element or as a packet networkelement.) This is in contrast to prior art network architectures inwhich a network element can be either TDM or packet, but not both. Thus,this aspect of the invention provides a more versatile, cost effectivearchitecture. It should also be noted that the selection of how thehybrid network elements are configured to carry traffic (TDM, packet, orboth) can be changed over time to meet requirements for more, less, orno traffic of one or the other type. The change can be dynamicallydetermined by monitoring traffic patterns over the network. Exemplarytechniques for implementing the non-BLSR protected layer 2/3 channel inthe hybrid network elements are described later herein with reference toFIG. 10.

Time Slot Allocation

Two-Fiber BLSR

In standard two-fiber BLSR, the fiber is split in half in the sense thatthe “upper” half of the channels are working and the “lower” areprotecting. In particular, the working time slot X is protected byprotection time slot X+N/2, where 1<=X<=N/2 and N is the total number oftimeslots in the fiber.

FIGS. 4 a-4 c are conceptual diagrams illustrating allocation oftimeslots over an optical ring according to various embodiments of theinvention. FIG. 4 a is a conceptual diagram illustrating the allocationof bandwidth of an optical fiber according to one embodiment of theinvention. FIG. 4 a corresponds to the example configuration oftimeslots shown in Table 1. TABLE 1 Configuration of Timeslots forchannels Channels Timeslots non-BLSR protected layer 2/3 1 non-BLSRprotected layer 2/3 . . . non-BLSR protected layer 2/3 N/2 − 1 WorkingN/2 non-BLSR protected layer 2/3 N/2 + 1 non-BLSR protected layer 2/3 N− 1 Protection N

In Table 1, timeslot N/2 is configured as the working channel 403.Timeslot N is configured as a protection channel 405. Timeslots 1through N/2−1 and timeslots N/2+1 through N−1 are configured as non-BLSRprotected Layer 2/3 channel 401. Thus, the scheme of Table 1 remainstrue to the standard BLSR working and protecting channel split. As aresult, non hybrid typical TDM elements can be put on the ring—i.e.compatibility exists between hybrid and non-hybrid TDM elements on theBLSR.

With reference to FIG. 4 a and Table 1, the time slots allocated to thenon-BLSR protected layer 2/3 channel are not contiguous, and thereforecannot be concatenated by the prior art. However, another aspect of theinvention provides for fragmented concatenations. Such fragmentedconcatenations allow for the logical concatenation of time slots thatare not physically contiguous. Specifically, whereas in standard BLSRthe concatenations are indicated in the SONET frames and are limited tophysically contiguous STSs, another aspect of the invention is theinclusion in the hybrid network elements the ability to be configured ina manner that allows the programming of fragmented concatenations. Thus,at the time the non-BLSR protected layer 2/3 channel is set up aroundthe ring, the fragmented concatenations are programmed in the hybridnetwork elements of the ring.

With respect to Table 1, the fragmented concatenations allow the hybridnetwork elements to treat the non-BLSR layer 2/3 time slots as being asingle concatenation even though they are separated by the protectionchannel. This allows a single large pipe to be formed for the non-BLSRprotected layer 2/3 channel as in FIGS. 4 a and 4 b, while stillallowing for conformity with the existing BLSR standard. As a result, anon-hybrid TDM network element, supporting non-preemptable unprotectedchannels, could be inserted into the ring (the only limitation is thatthe non-BLSR protected layer 2/3 TDM traffic cannot enter or exit thering at the non-hybrid TDM network element; that traffic must only passthrough). Exemplary techniques for implementing the fragmentedconcatenations in the hybrid network elements are described later hereinwith reference to FIG. 10. A more detailed description of fragmentedconcatenations can be found in a patent application titled “Any Size andLocation of Concatenated Packet Data Across Sonet Frames in a SonetSignal” to Anurag Nigam and David Stiles, filed on Dec. 29, 2000, Ser.No: 09/751,764, Attorney Docket Number: 004906.P014, which is herebyincorporated by reference.

Providing a single large pipe for layer 2/3 TDM traffic throughconcatenations increases the efficiency of transmission and managementof the Layer 2/3 TDM traffic. A single large pipe also simplifies thetask of processing variable length packets.

Two exemplary alternative mechanisms for achieving single concatenatedchannels are referred to herein as inverted and paired channelprotection schemes. Neither is in conformance with standard BLSR.

FIG. 4 b is a conceptual diagram of the division of bandwidth accordingto a paired channel protection scheme on an optical fiber according toone embodiment of the invention. In FIG. 4 b, the bandwidth of an Easttransmit fiber 410 is divided between a non-BLSR protected Layer 2/3channel 401, a working channel 403 and a protection channel 405. Thedivision of bandwidth of the East transmit fiber 410 corresponds to theexample configuration of timeslots illustrated by Table 2. Table 2 showstimeslot 1 configured as the working channel 403 and timeslot 2configured as the protection channel 405. TABLE 2 Configuration ofTimeslots for channels Channels Timeslots Working 1 Protection 2non-BLSR protected layer 2/3 3 non-BLSR protected layer 2/3 4 non-BLSRprotected layer 2/3 . . . non-BLSR protected layer 2/3 . . . non-BLSRprotected layer 2/3 N

In Table 2, timeslots 3 through N (N being the total number oftimeslots) are configured as the non-BLSR protected Layer 2/3 channel401.

FIG. 4 c is a conceptual diagram illustrating the allocation ofbandwidth of the fiber in accordance with an inverted channel protectionscheme according to one embodiment of the invention. The bandwidthallocation illustrated by FIG. 4 c corresponds to the exampleconfiguration of timeslots shown in Table 3. TABLE 3 Configuration ofTimeslots for channels Channels Timeslots Working 1 non-BLSR protectedlayer 2/3 2 non-BLSR protected layer 2/3 . . . non-BLSR protected layer2/3 . . . non-BLSR protected layer 2/3 . . . non-BLSR protected layer2/3 N − 1 Protection N

In Table 3, timeslot 1 is configured as the working channel 403.Timeslot N is configured as the protection channel 405. Timeslots 2through N−1 are configured as the non-BLSR protected Layer 2/3 channel401.

Four-Fiber BLSR

In 4 fiber BLSR, two non-BLSR protected layer 2/3 channels areprovisioned over the ring as in 2 fiber BLSR conforming to standard BLSRtime slot allocation. One non-BLSR protected layer 2/3 channel isprovisioned on the fiber with the working channel. The other non-BLSRprotected layer 2/3 channel is provisioned on the fiber with theprotection channel. In one embodiment of the invention, traffic isconcatenated for each non-BLSR protected layer 2/3 channel. In anotherembodiment, fragmented concatenation can be extended for utilization in4 fiber BLSR.

Furthermore, a load balancing mechanism (e.g., ATM SAR, multi-link PPP,etc.) would be implemented in a 4 fiber BLSR to balance traffictransmitted over a channel spanning multiple fibers.

The allocation of bandwidth for channels can be adjusted to servicedemand. If TDM traffic is the dominant traffic on the carrier's network,then a larger number of timeslots will be configured for working andprotection channels. If layer 2/3 TDM traffic dominates the carriernetwork, then more timeslots will be configured for the non-BLSRprotected Layer 2/3 channel.

Exemplary Techniques for Protecting the Non-BLSR Protected Layer 2/3Channel Traffic

Although the non-BLSR Layer 2/3 channel is not protected by standardBLSR, there are a number of different ways in which the non-BLSR Layer2/3 channel traffic can be protected. For example, in one embodiment,the Layer 2 or 3 forms of protection can be relied upon. If Layer 3protection by routing protocols is relied upon, it should be understoodthat the response time for a protection switch will be significantlylonger than the reaction time of standard BLSR. The routing protocolswill discover the failure and route traffic around it. Typically,detection of a failure is done with time-outs. However, it is possiblefor the layer 1 SONET protocol to notify the layer 3 routing protocol offailures, greatly improving the speed at which layer 2/3 recover isdone. While one embodiment relies on standard Layer 2 and/or 3 forms ofprotection, alternative embodiments of the invention rely on other typesof protection that achieve the speed of the protection switch providedby standard BLSR.

In one embodiment in which all the network elements in the ring need notbe hybrid network elements, the hybrid network elements on the ring areconfigured to have a corresponding multiprotocol label switching (MPLS)tunnel for the traffic on the non-BLSR protected Layer 2/3 channel thatis to be “Layer 2/3 BLSR protected.” Based on a failure being identifiedby the BLSR section of the hybrid network elements, the layer 2/3section of the network elements sharing the span on which the failureoccurred switch to forward out the preconfigured MPLS tunnels. Since thetunneled traffic is statistically multiplexed with traffic in thenon-BLSR protected layer 2/3 channel, the protecting tunnels may bepreconfigured, but they still follow standard BLSR routes through thering.

FIG. 5 is a flowchart for providing an alternative path for protectingnon-BLSR protected Layer 2/3 TDM traffic in BLSR protection time usingLayer 2/3 BLSR protection according to one embodiment of the invention.FIG. 3 e is a diagram of exemplary traffic flow while there is and isnot a failure in the six node ring illustrated in FIG. 3 a wherein anon-BLSR protected Layer 2/3 channel is protected using Layer 2/3 BLSRprotection according to one embodiment of the invention. FIG. 3 e showsgenerally the same elements as FIG. 3 d, with the exception of a tunnel360 described below. FIG. 5 and 3 e will be described together.

At block 501, a tunnel is configured on each network element in anoptical ring. With reference to FIG. 3 e, the system is configured totransmit layer 2/3 traffic 353 from node 301 to node 303 over thenon-BLSR protected channel 323 of node 301's West transmit fiber 319. Inthis example, the layer 2/3 traffic 353 exits the ring to an externalnetwork element at node 303. A tunnel 360 is configured to travelthrough the non-BLSR protected channel 323 around the ring in theopposite direction to terminate in node 303. In one embodiment, thistunnel is configured as an MPLS tunnel because MPLS tunnels can beconfigured to have variable bandwidth (that is the pipe size maximum canbe entered, but the pipe will only take what bandwidth is needed fromzero up to the maximum).

At block 503, a logical working interface is configured on one of thenetwork elements of the ring and associated to a physical interface.Typically an interface is synonymous with a physical port. A logicalinterface is an abstraction or data structure representation of thephysical port. Multiple logical interfaces can be associated to a singlephysical port. With reference to FIG. 3 e, the logical working interfaceon node 301 is configured for the layer 2/3 traffic 353 to forward it tothe physical port for node 301's east transmit fiber 313.

At block 505, the previously configured tunnel is configured as alogical protection interface on the network element. With reference toFIG. 3 e, a logical protection interface on node 301 is configured forthe layer 2/3 traffic 353 to forward it to the tunnel configured on thephysical port for node 301 s west transmit fiber 319.

At block 506, a logical interface is configured and associated to thelogical working interface and logical protection interface. The logicalinterface is initially configured to point to the logical workinginterface.

At block 507, the network element determines if a failure has beendetected on the fiber coupled to the physical interface. If a failure isnot indicated by a BLSR state machine, then at block 509 traffic isforwarded with the logical working interface as usual. If a failure isindicated by the BLSR state machine, then at block 510, the logicalinterface is switched from the logical working interface to the logicalprotection interface. With reference to FIG. 3 e, the logical interfaceis switched to the protection interface so that the layer 2/3 traffic353 is forwarded out the tunnel 360 over node 301's west span. As such,the layer 2/3 traffic 353 is protection switched using layer 2/3 BLSRprotection at the speed of standard BLSR, without using standard BLSR.In addition, the tunnel 360 is statistically multiplexed with the layer2/3 TDM traffic 357 being transmitted over the non-BLSR protected layer2/3 channel 323 on node 301's west span 319.

Thus, in an embodiment in which a variable size MPLS tunnel is used,when there is no failure the tunnel is of size zero and the fullbandwidth of the non-BLSR protected layer 2/3 channel on node 301's westspan 319 is available for the layer 2/3 TDM traffic 357. However, on afailure, that bandwidth is shared with the tunnel 360 via thestatistical multiplexing provided by the packet switching mechanism.

At block 511 the network element forwards traffic through the logicalprotection interface which is the tunnel. Since the non-BLSR protectedlayer 2/3 channel carries more traffic while there is a failure thenwhile there is not a failure, a mechanism is implemented in certainembodiments to allocate the bandwidth. In one embodiment, a fairnessscheme is implemented (e.g., so that 60% of the tunneled traffic is highpriority traffic and 60% of the non-tunneled traffic is high priority).In another embodiment, a priority scheme would place a limit on theamount of tunneled traffic or non-tunneled traffic transmitted over thenon-BLSR protected layer 2/3 channel when a failure occurs. In anotherembodiment of the invention, the tunneled and non-tunneled traffic aretreated equally with respect to the physical bandwidth. In such anembodiment, if congestion occurs, then a determination to transmit ismade or a packet by packet basis. This determination is made based uponpriority indicated by each packet.

At block 513, a routing protocol calculates a different path for thetraffic due to the failure. After a new path is calculated, theforwarding table(s) of the network element and/or a different networkelement is updated at block 515. With reference to FIG. 3 e, theforwarding tables in the nodes 301, 307, 309, 311, and 305 may beupdated to provide the layer 2/3 TDM traffic 353 to the node 303.Alternatively, the forwarding tables in network elements external to thering may be updated to transmit the layer 2/3 TDM traffic to the node303 over a route that does not include the ring of FIG. 3 e.

At block 517, traffic is forwarded to a new interface based on the tableupdate performed at block 515.

At block 521 the network element switches the logical interface back tothe logical working interface. Block 521 can be implemented to beperformed responsive to a number of different stimuli (e.g., 1) acorrection of the failure; 2) a predetermined amount of time [typicallythe time expected to be required for blocks 511-515 to be completed; 3)detection that traffic is no longer being sent over the tunnel[indicating that the blocks 511-515 have been completed], etc.). Withreference to FIG. 3 e, the logical interface is switched back to theworking interface; therefore, if and when traffic is sent to the logicalinterface, it will be transmitted out the working interface over thenon-BLSR protected layer 2/3 channel of node 301's east span 313. Assuch, the tunnel traffic will drop down to zero. Thus, in an embodimentusing a variable MPLS tunnel, the bandwidth used by the tunnel willshrink back to zero.

After the failure is corrected (e.g., the fiber is restored, fiberreplaced, etc.), the routing protocol will determine that a better pathavailable, the better path being the original path. The network elementswill converge and the forwarding tables will be updated. Since theoriginal path was the best path, then the logical interface on node 301should be the interface to the node 303.

In one embodiment of the invention, a data structure indicates a tunneland the parameters for the tunnel. A second data structure indicates aphysical interface and the physical parameters for the interface. Athird data structure indicates a logical interface and stores a pointerto the second data structure and a pointer to the tunnel data structure.Traffic is processed with the logical interface which initially followsthe pointer to the second data structure. When the BLSR state machineindicates a failure, the network element will activate the tunnelstructure pointer in the logical working interface. Traffic forwardedthrough the logical interface will be processed with the data stored inthe tunnel data structure. The tunnel would of course run opposite thedirection of the ring failure.

In another embodiment of the invention, a data structure would beindexed by the logical interface identifier. The logical interface wouldindex a tunnel name, a physical interface, and a protection bit. Trafficto be forwarded through the logical interface would be processed withthe data associated to the physical interface. Upon a ring failure, thenetwork element would switch the projection bit. Traffic to be forwardedthrough the logical interface would now be processed with the dataassociated to the tunnel name because the protection bit indicates afailure in the working interface channel. These illustrations areintended to aid in the understanding of the invention and not meant tobe limiting upon the invention.

In another embodiment, rather than using tunnels, the forwarding tablesfor the packet switch in each of the hybrid network elements on the ringinclude failure mode entries in addition to the typical forwardingentries (normal mode entries). Based on a failure being identified bythe BLSR section of the hybrid network elements, the layer 2/3 sectionof the network elements switch to the failure mode entries. When thefailure is corrected, the layer 2/3 section of the network elementswitches back to the normal mode entries.

In an embodiment of the invention, a ring is formed from hybrid networkelements, as well as network elements which appear as regenerators atlayer 2 and layer 3, but appear as participants in the BLSR ring atlayer 1. The hybrid network elements manage layer 2/3 forwarding tablesand a cross-connect table which interact. The layer 2/3 forwardingtables reference working interfaces and protecting interfaces. Thenon-hybrid network elements manage cross connect tables. When there isno failure, traffic may be switched through the packet mesh of a hybridnetwork element and transmitted as TDM traffic through the cross connectof a non-hybrid network element. In one embodiment of the invention,while there is a failure, the hybrid network elements update their crossconnect tables and their layer 2/3 forwarding tables. In anotherembodiment of the invention, while there is a failure, the hybridnetwork elements update logical interfaces and their cross connecttables. The non-hybrid network elements update their cross connecttables. Protection switched traffic may be transmitted through thepacket mesh to a protection interface in hybrid network elementsadjacent to the failure, but pass through the cross connect on theprotection channel of non-hybrid network elements and mid-span hybridnetwork elements. It should be understood that for various reasons, ahybrid network element may be programmed to behave as a non-hybridnetwork element in certain environments.

The owner of the ring can provide multiple services with the tunnelprotected non-BLSR protected layer 2/3 channel. The owner of the ringcan offer the bandwidth allocated to the non-BLSR protected layer 2/3channel as a maximum bandwidth and a guaranteed bandwidth in accordancewith a priority scheme. The owner of the ring can implement a priorityscheme to support a guaranteed bandwidth of half the non-BLSR protectedlayer 2/3 channel, 20% of the non-BLSR protected layer 2/3 channel, etc.

Additional Embodiments that Provide Different Types of Service

Having described a non-BLSR protected layer 2/3 channel, another aspectof the invention is the configuring a non-BLSR protected layer 2/3channel and a variable rate layer 2/3 pipe on a single physical opticalring. In order to describe this, the configuring of just a variable ratelayer 2/3 pipe on a BLSR will first be discussed. This will be followedby a description of the configuring of both a non-BLSR protected layer2/3 channel and a variable rate layer 2/3 pipe on the same physicaloptical ring.

A Variable Rate Layer 2/3 TDM Traffic Pipe

FIG. 6 is a conceptual diagram illustrating an exemplary division of anoptical span's bandwidth according to one embodiment of the invention.In FIG. 6, the optical span's 601 bandwidth is evenly split between aworking channel 603 and a protection channel 605. A segment of bandwidth607 in the working channel 603 will carry TDM traffic. This segment ofbandwidth 607 will be referred to as the working TDM pipe. While thereis not a failure, the remaining bandwidth 609 of the working channel 603forms a subpipe, all of the protection channel 605 forms a subpipe, andtogether these subpipes form a layer 2/3 pipe to transmit TDM traffichaving layer 2/3 traffic (ATM, Ethernet, Frame Relay, Internet Protocol,etc.) as payload. While there is a failure, the segment of bandwidth 613of the protection channel 607 will carry a protection switched stream ofTDM traffic. The segment of bandwidth 611 of the protection channel 607will be used as a protecting layer 2/3 subpipe to carry another streamof protection switched TDM traffic. The segment of bandwidth or workinglayer 2/3 subpipe 609 of the working channel 603 will carry the TDMtraffic having layer 2/3 traffic as payload transmitted in the layer 2/3pipe while there is not a failure.

FIGS. 7 a-7 c are diagrams illustrating example traffic flow while thereis and is not a failure on an optical span according to one embodimentof the invention. FIG. 7 a is a diagram illustrating an example trafficflow while there is not a failure in an optical span according to oneembodiment of the invention. In FIG. 7 a, a West transmit span 701 isdivided into a working channel 705 and a protection channel 707. In FIG.7 a, the West transmit span 701 carries two streams of traffic. In aworking TDM pipe 702 the West transmit span 701 carries a stream of TDMtraffic 709. The West transmit span 701 carries another stream of TDMtraffic 711 having layer 2/3 traffic as payload in a layer 2/3 pipe 712.The stream of TDM traffic 711 is represented by two lines to show thelayer 2/3 pipe 712 encompassing a segment of the working channel 705 andall of the protection channel 707 (it should be noted that the layer 2/3pipe need not encompass all of the protection channel 707—some of thischannel could go unused and/or some of this channel could be used for adifferent purpose, e.g., extra traffic).

In FIG. 7 a, an East transmit span 703 is also divided into a workingchannel 706 and a protection channel 708. The East transmit span 703carries two streams of traffic. In a working TDM pipe 704 the Easttransmit span 703 carries a stream of TDM traffic 717. The East transmitspan 703 carries another stream of TDM traffic 719 having layer 2/3traffic as payload in a layer 2/3 pipe 714. The stream of TDM traffic719 is represented by two lines to show the layer 2/3 pipe 714encompassing a segment of the working channel 706 and all of theprotection channel 708 (again, it should be noted that the layer 2/3pipe need not encompass all of the protection channel 707).

The streams of TDM traffic 711 and 719 carry data traffic formattedaccording to a layer 2/3 protocol such as ATM, Ethernet, Frame Relay,Internet Protocol, etc as payload. The streams of TDM traffic 711 and719 can be transmitted in a number of scenarios. The streams of TDMtraffic 711 and 719 may be switched into the ring through the packetswitching mechanism in one node and exit the ring as TDM traffic fromanother node. The streams of TDM traffic 711 and 719 may be switchedinto the ring as layer 2/3 traffic through the packet switchingmechanism in one node and exit the ring through the packet switchingmechanism in another node in the form of layer 2/3 traffic. Theseexamples are described as illustrations to aid in understanding theinvention and not meant to be limiting upon the invention.

FIG. 7 b is a diagram illustrating an example traffic flow while thereis a failure in an optical span according to one embodiment of theinvention. In FIG. 7 b, the East transmit span 703 fails (e.g. a severedline, failing hardware, etc.). The West transmit span 701 continues tocarry the stream of TDM traffic 709 in the working TDM pipe 702. TheWest transmit span 701 also continues to carry the stream of TDM traffic711 having layer 2/3 traffic as payload, but only in a working layer 2/3subpipe 733. A protecting layer 2/3 subpipe 735 now carries the streamof TDM traffic 719 having layer 2/3 traffic as payload because alltraffic traveling in the working channel 706 of the East transmit span703 prior to the failure was protection switched to the protectionchannel 707 of the West transmit span 701. The East stream of TDMtraffic 717 now travels in the protecting TDM pipe 710 of the Westtransmit span 701. The West protecting TDM pipe 710 is the same size ornumber of timeslots as the working TDM pipe 704.

As shown in the illustration of FIGS. 7 a and 7 b, the streams of TDMtraffic 709 and 717 are transmitted at a constant rate because theyutilize the same amount of bandwidth while there is not and is afailure. In contrast, the streams of TDM traffic 711 and 719 aretransmitted at a variable rate. While a failure does not exist, bothstreams of TDM traffic 711 and 719 are transmitted over the layer 2/3pipe which is allocated a large segment of bandwidth including some ofthe working channel and all of the protection channel timeslots. While afailure exists, the streams of variable rate TDM traffic 711 and 719 aretransmitted over layer 2/3 subpipes which are allocated an equal amountof the timeslots not used by the constant rate T)M traffic 709 and 717.

The variability in the pipe size is possible because of the statisticalmultiplexing capability of the packet switching mechanism in the networkelements of the ring. Specifically, the reduction in the amount ofavailable bandwidth for the TDM traffic having layer 2/3 traffic aspayload requires the packets switch of the network element to bufferand/or to drop layer 2/3 traffic to make that traffic fit the providedpipe.

FIG. 7 c is a diagram of the example traffic flow 719 of FIGS. 7 a and 7b while there is not and is a failure of the span 703 of FIGS. 7 a and 7b in a ring according to one embodiment of the invention. In FIG. 7 c,three nodes 731, 739, and 741 connect to each other to form an opticalring. Each node in a ring has a West and East transmit span, but in FIG.7 c only the East and West transmit spans from the node 731 and an Easttransmit span from the node 739 are shown. The West transmit span 701carries traffic from node 731 to node 739. The East transmit span 703carries traffic from the node 731 to the node 741. The East transmitspan 740 carries traffic from the node 739 to the node 741. Aspreviously shown in FIG. 7 a, the variable rate TDM traffic 719 travelsover the layer 2/3 subpipe 714 to node 741. Once node 731's Easttransmit span 703 fails, the variable rate TDM traffic 719 travels overthe protecting layer 2/3 subpipe 735. Since the variable rate TDMtraffic 719 is destined for node 741, the variable rate TDM traffic 719is switched through node 739 and travels along node 739's East transmitspan 740 in its protecting layer 2/3 subpipe 743. Node 739 knows totransmit the variable rate TDM traffic 719 onto a protecting layer 2/3subpipe because node 731 has communicated to 739 a protection switch.

As an illustration of the protection switch in relation to end users,assume that traffic from a first, second ,and third user enter the ringillustrated in FIG. 7 c at node 731. Also assume that the first andsecond user's traffic is to be terminated at node 741 and exit the ringat node 741 to an external network element. The third user is to beterminated at node 739 and exit the ring to an external network element.The traffic from all three users is transmitted over the layer 2/3 pipefrom node 731 to node 741. The traffic from the third user is switchedthrough the packet mesh of node 741 and transmitted over a second layer2/3 pipe (not shown) between node 741 and node 739. As before, assumethat there is a failure of span 703. While there is this failure, thetraffic in the layer 2/3 pipe 714 is switched to the protecting layer2/3 pipe 735. The traffic from all three users is passed through thecross connect of node 739 and terminated at node 741. The traffic fromthe first and second users exit the ring at node 741 while the trafficfrom the third user is switched through the packet mesh of node 741 andtransmitted back to node 739 over the working subpipe of the secondlayer 2/3 pipe (not shown).

As illustrated in FIG. 7 c, a failure on the ring does not cause theloss of the traffic on the layer 2/3 pipe, just a reduction in theavailable bandwidth. This is because the layer 2/3 pipe is madepartially from the working channel and partially from the protectionchannel. As such, this layer 2/3 pipe is more sellable to customers thanthe extra traffic described in the background section because a failuredoes not result in a total loss of service. Moreover, using the BLSRprotection scheme enables the traffic traveling in the layer 2/3 pipe tobe protection switched in a 50 millisecond time frame.

To provide an example of the manner in which the layer 2/3 pipe could besold, assume that the working and protection channel parts of the layer2/3 pipe 714 are respectively 30 mbps and 90 mbps. Assume, that each ofthe first, second and third users above want an equal amount ofbandwidth of the layer 2/3 pipe 714. Each customer could be offered aguaranteed (in the event of a single failure) 10 mbps and a maximum of40 mbps. The customers traffic at node 731 would be statisticallymultiplexed to fit the size of the layer 2/3 pipe currently beingprovided. The guaranteed 10 mbps per customer would be provided by theworking subpipe on span 703 or the protecting layer 2/3 subpipe 735. Themaximum 30 mbps per customer would be provided by the protection subpipeon span 703 when there is no failure. In this manner partially BLSRprotected layer 2/3 traffic is provided around the ring.

It should be understood that the ability to offer a guaranteed minimumbandwidth requires that the bandwidth of the layer 2/3 pipes on the ringnot be oversold. Thus, in the above example, to offer the third user theservice identified above, the ring provider would also have at least theneeded bandwidth (guaranteed 10 mbps and a maximum of 40 mbps) on thesecond layer 2/3 pipe from node 741 to node 739 (not shown) because thethird users traffic must traverse that span as well as span 703. Inother words, if a potential user's traffic must traverse multiple spansof the ring in layer 2/3 pipes, each of these layer 2/3 pipes must haveavailable the necessary bandwidth. Although the first, second, and thirdcustomers are each given a guaranteed bandwidth of 10 Mbps, it ispossible for any of them to transmit greater than their guaranteedamount as long as others are transmitting less than their guaranteedamount. The total bandwidth cannot exceed 30 Mbps, but this amount canbe divided arbitrarily as long as the guaranteed amounts hold.

It should also be noted that not every network element in the ring needto be of the type that is capable of both TDM and packet switching (ahybrid network element). Intermediate nodes that do not switch trafficout of the ring can be standard non-hybrid network elements. Thus,compatibility is maintained.

FIG. 10 is a diagram of circuit components in a hybrid network elementaccording to one embodiment of the invention. While in this embodimentseparate switching mechanisms are provided for the TDM and packetswitching (namely a TDM switch fabric and a packet mesh), alternativeembodiments could provide a single switching mechanism and/or differentswitching mechanisms (e.g., a packet switch fabric, a TDM mesh, etc.).In FIG. 10, four optical transmit fibers 1015, 1002, 1006, 1010 connectto physical ports 1011, 1014, 1018, and 1022 respectively. Four opticalreceive fibers 1017, 1004, 1008, and 1012 connect to physical ports1013, 1016, 1020, and 1023 respectively. TDM traffic is received overthe optical receive fibers 1017, 1004, 1008, 1012 and transmitted overthe physical ports 1011, 1014, 1018, 1022. The TDM traffic istransmitted and received as optical signals by physical connectioncircuitry (PCC) 1001, 1007, 1003, 1005. The PCCs convert optical signalsto electrical signals and vice versa for reception and transmission. TheTDM traffic is transmitted and received between the PCCs 1001, 1007,1003, 1005 and the TDM processing circuits (TPCs) 1019, 1031, 1025, and1037 respectively as electrical signals. The TPCs transmit and receiveTDM traffic from a control card (CC) 1009. In another embodiment of theinvention, each TPC and PCC is located on a single processing element,such as an application specific integrated circuit (ASIC).

The layer 2/3 traffic can be switched through the CC 1009 or a packetmesh 1050. The TPCs are programmable to insert and extract particularSTSs that carry layer 2/3 traffic to be packet switched. If TDM trafficcontains layer 2/3 payload to be switched through the packet mesh 1050,then the TPCs 1019, 1031, 1025, and 1037 extract the layer 2/3 payloadtraffic from the TDM traffic and transmit the layer 2/3 traffic toingress layer 2/3 processing circuitry 1021, 1033, 1027, and 1039respectively. The TPCs 1019, 1031, 1025, and 1037 also receive layer 2/3traffic from egress layer 2/3 processing circuitry 1021, 1033, 1027, and1039 respectively. For a variable rate layer 2/3 traffic pipe, theegress layer 2/3 processing circuitry includes the ability to queue andstatistically multiplex layer 2/3 traffic before transmitting it to aTPC. The TPCs 1019, 1031, 1025, and 1037 process the layer 2/3 trafficplacing it into SONET/SDH frames for transmission in timeslots. The TPCs1019, 1031, 1025, and 1037 are programmable to insert and extractparticular STSs that carry the layer 2/3 traffic to be packet switched.

The CC 1009 detects failures, maintains a BLSR state machine, andupdates the TDM cross connect table in response to changes in the BLSRstate machine. The CC 1009 also sends a message to update the layer 2/3forwarding tables for the packet BLSR protection switching. In addition,the CC 1009 sends messages to reprogram the TPCs to handle a protectionswitch (e.g., reorient concatenations, redirect channels to packet meshand CC, etc.).

To provide an example of the reprogramming of the network elements tohandle a ring switch, assume that the ring of FIG. 7 c is a 2 fiberOC-12 BLSR (that is, 6 STSs for working and 6 STSs for protection ineach direction). Also assume that each of the nodes of FIG. 7 c isimplemented as the network element illustrated in FIG. 10; that the PCC1001 of a given node is connected through fiber to the PCC 1003 of theadjacent node; that the fibers 1015 and 1006 are the transmit fibers;that the PCC 1003 of node 731 is connected through fiber to PCC 1001 ofnode 741; and that the fibers 1017 and 1008 are the receive fibers.Table 1 below illustrates the concatenations and the redirection of STSsprogrammed in the TPCs 1019 and 1025 of each node while there is not andis a failure on span 703. While There is Not a Failure While There is aFailure Node TDM Layer 2/3 Pipe TDM Layer 2/3 Pipe 731 On TPC 1019 OnTPC 1019 On TPC 1019 On TPC 1019 for transmit for transmit for transmitfor transmit fiber 1015: X fiber 1015: STS fiber 1015: X fiber 1015: STSon channels 1-4, 2C on channels on channels 1-4; 2C on channels where Xis 5-6; STS 6C on STS 1 on 5-6; STS 2C on some particular channels 7-12channel 7 channels 11-12 arrangement On TPC 1025 protecting protectinglayer On TPC 1025 for transmit TDM; 2/3 subpipe for transmit fiber 1006:STS STS 3C on On TPC 1025 fiber 1006: STS 2C on channels channels 8-10for transmit 1 on channel 1; 5-6; STS 6C on TDM fiber 1006: Nothing STS3C on channels 7-12 On TPC 1025 channels 2-4 for transmit fiber 1006:Nothing 741 On TPC 1019 On TPC 1019 On TPC 1019 On TPC 1019 for receivefiber for receive fiber for receive fiber for receive fiber 1017: STS 1on 1017: STS 2C 1017: Nothing 1017: Nothing channel 1; on channels 5-6;On TPC 1025 On TPC 1025 STS 3C on STS 6C on for receive fiber forreceive fiber channels 2-4 channels 7-12 1008: Y on 1008: STS 2C On TPC1025 On TPC 1025 channels 1-4; on channels 5-6; for receive fiber forreceive fiber STS 1 on STS 2C on 1008: Y on 1008: STS 2C channel 7channels 11-12 channels 1-4, on channels 5-6; protecting protectinglayer where Y is STS 6C on TDM; 2/3 subpipe some particular channels7-12 STS 3C on arrangement channels 8-10 protecting TDM 739 On TPC 1019On TPC 1019 On TPC 1019 On TPC 1019 for transmit for transmit fortransmit for transmit fiber 1015: Y fiber 1015: STS fiber 1015: Y fiber1015: STS on channels 1-4 2C on channels on channels 1-4; 2C on channelsOn TPC 1025 5-6; STS 6C on STS 1 on 5-6; STS 2C on for receive fiberchannels 7-12 channel 7 channels 11-12 1008: X on On TPC 1025 protectingprotecting layer channels 1-4 for receive fiber TDM; 2/3 subpipe 1008:STS 2C STS 3C on On TPC 1025 on channels 5-6; channels 8-10 for receivefiber STS 6C on protecting 1008: STS 2C channels 7-12 TDM on channels5-6; On TPC 1025 STS 2C on for receive fiber channels 11-12 1008: X onprotecting layer channels 1-4; 2/3 subpipe STS 1 on channel 7 protectingTDM; STS 3C on channels 8-10 protecting TDM

In addition to the reprogramming of the TPCs, the cross connect tablesand the forwarding tables are altered accordingly. As in the exampledescribed above, traffic for three users enter the ring at node 731 ofFIG. 7 c. The traffic from these three users are switching into the ringin node 731 from the PCC 1007 through the packet mesh 1050. While thereis not a failure, the traffic from all three users is transmitted fromthe IL2/3PC 1033 across the packet mesh to the EL2/3PC 1029 according tothe forward tables and transmitted in the layer 2/3 pipe by TPC 1025.While there is a failure of the fibers connecting into 731's PCC 1003,the forwarding tables are modified so that the traffic from the threeusers is switched through the packet mesh from IL2/3PC 1033 through thepacket mesh 1050 to the EL2/3PC 1023 and transmitted in the protectinglayer 2/3 pipe to node 739 by the TPC 1019 which has been reprogrammedas described above.

In node 739, the forwarding tables are modified because of the failureso that the traffic for the three users received from node 731 on node739's PCC 1003 in the protecting layer 2/3 channel is switched throughthe packet mesh 1050 from the IL2/3PC 1027 to the EL2/3PC 1023 andtransmitted to node 741 in the protecting layer 2/3 channel by the TPC1019 which has been reprogrammed for the failure.

In node 741, the forwarding tables are modified because of the failureso that the traffic for users 1 and 2 received from node 739 on node 741's PCC 1003 is switched through the packet mesh 1050 from the IL2/3PC1027 to the EL2/3PC 1041 and transmitted out of the ring through the PCC1005. The traffic for the third user is switched through the packet meshfrom the IL2/3PC 1027 to the EL2/3PC 1029 and transmitted out the PCC1003 on the working layer 2/3 channel to node 739 by the TPC 1025. Thetraffic from the third user is received at node 739 at the PCC 1001 onthe working layer 2/3 channel and switched through the packet mesh 1050from the IL2/3PC 1021 to the EL2/3PC 1041 in accordance with theforwarding tables and transmitted out of the ring by the PCC 1005.

A four fiber BLSR can perform a span switch or ring switch depending onthe type of failure in the ring. The forwarding tables and cross connecttables of the nodes in the ring must be updated in accordance with thetype of protection switch performed in the 4 fiber BLSR ring. Theconcatenations must also be reoriented and channels redirectedaccordingly.

FIG. 8 is a flowchart for allocating a layer 2/3 pipe and subpipes in anoptical ring according to one embodiment of the invention. At block 801,a network administrator configures timeslots as working and protectionchannels on each node of a ring. At block 803, the network administratordetermines which timeslots will be processed as layer 2/3 traffic andwhich timeslots will be processed as TDM traffic. At block 805, a TDMprocess running on a control card of a node in the ring detects afailure in one of the node's spans. The TDM process updates a TDM crossconnect forwarding table managed on the control card at block 807. Atblock 809, the TDM process sends a message to a layer 2/3 processindicating the failure. The layer 2/3 process updates a protectioninterface table in response to the message from the TDM process at block811. At block 813, the node communicates the failure to other nodes inthe ring. At block 815, the other nodes in the ring updates their crossconnect tables in accordance with the failure detected by the detectingnode. In another embodiment of the invention, the tables updated atblock 815 include the cross connect table and the layer 2/3 forwardingtables.

In one embodiment of the invention, the protection interface table is adata structure with a reference to a logical working interface and alogical protection interface. The logical working interface correspondsto a physical port connecting to a transmit fiber to carry trafficdestined for a node X going in a preferred direction on the ring. Thelogical protection interface corresponds to another physical portconnected to a transmit fiber destined for the node X, but going in theopposite direction and possibly through other nodes in the ring. Alogical interface stored in a layer 2/3 forwarding table initiallyrefers to the logical working interface while there is not a failure.While there is a failure, the logical interface refers to the logicalprotection interface. When the failure is corrected, the logicalinterface is reset to refer to the logical working interface. In anotherembodiment of the invention, a routine manages logical interfaces andanother routine manages alternate interfaces. A network administratorconfigures alternate interfaces on a network element. The alternateinterface manager will create a data structure to refer to 2 logicalinterfaces which are managed by the interface manager. One of theinterfaces will be the working interface while the other interface willbe the protecting interface. In the layer 2/3 forwarding table, acircuit identifier is associated to either a logical interface or aalternate interface. Upon a failure notification, the alternateinterface manager will alter the data structure to reference the logicalinterface acting as the protecting interface. In another embodiment ofthe invention, the TDM process instead of the layer 2/3 process updatesa data structure indicating protection interfaces.

The owner of the optical ring can now offer protected service tomultiple customers. Typically, only the traffic traveling in the workingchannel was sold to customers since consumers did not want to purchase aservice which may be interrupted (e.g., for days). Alternatively, aconsumer may choose to purchase at a reduced cost, the extra trafficservice from 2 providers. This consumer would alternate between theseproviders as failures occurred. With a layer 2/3 pipe, the owner of theoptical ring can offer multiple classes of service. In addition to thetraditional constant rate TDM traffic service, the network owner orprovider can offer a variable rate TDM traffic service to customersbecause the payloads are layer 2/3 units of traffic. For example, ifbandwidth corresponding to a layer 2/3 pipe transmits at a rate of 100megabits per second with 20 megabits corresponding to the layer 2/3subpipes, the owner or provider can offer a service guaranteeing a rateof 20 megabits per second with a maximum of 100 megabits per second.This variable rate service can be offered to multiple people since theTDM payloads are layer 2/3 units of traffic. In addition, the variablerate service can be offered with a BLSR protection time of 50milliseconds. Furthermore, the owner or provider of the optical network,is not forced to either donate or sell at a reduced cost 50% of theirbandwidth. The owner of provider can sell 100% of its bandwidth with thecombination of standard TDM service and the variable rate TDM service.

The techniques shown in the figures can be implemented using code anddata stored and executed on computers. Such computers store andcommunicate (internally and with other computers over a network) codeand data using machine-readable media, such as magnetic disks; opticaldisks; random access memory; read only memory; flash memory devices;electrical, optical, acoustical or other form of propagated signals(e.g., carrier waves, infrared signals, digital signals, etc.); etc. Ofcourse, one or more parts of the invention may be implemented using anycombination of software, firmware, and/or hardware.

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described. Although the invention has beendescribed with reference to the TDM form of optical switching, theinvention can be applied to any form of optical switching including wavedivision multiplexing, dense wave division multiplexing, etc usingvarious forms of optical ring protection. In addition, the invention hasbeen described with respect to a 2 fiber and 4 fiber BLSR, but can bescaled to other n-fiber architectures of BLSR.

Furthermore, while the invention has been described in terms ofswitching the traffic in the layer 2/3 pipe through the packet mesh ofeach node while there is not a failure, a variety of configurations arepossible for an optical ring with a layer 2/3 pipe. In a five node ring,a first node may have a layer 2/3 pipe defined over a direct connectionto a second node. The first node may also have a layer 2/3 pipe definedover a logical direct connection to a third node through the crossconnect of the second node. The first node may also have a layer 2/3pipe defined over a logical direct connection to a fifth node throughthe fourth node's cross connect. An optical ring may have 4 nodes whichare hybrid network elements and 2 nodes which are TDM only networkelements. The TDM only network elements may only act as regeneratorsbetween the hybrid network elements. A first hybrid node may have alayer 2/3 pipe defined to a second layer 2/3 pipe through a TDM onlynode. The first hybrid node may have a layer 2/3 pipe defined to the TDMonly node while a another layer 2/3 pipe is defined from the TDM onlynode to the second hybrid node. These examples are provided to aid inthe understanding of the invention and not meant to be limiting upon theinvention.

In addition, although the traffic that is passing through a given node(being provided to that node on a span of the ring and being transmittedby that node out another span of the ring) in layer 2/3 pipes may beswitched through the packet mesh of that node, the traffic is notconsidered to be terminated from the ring at that node, but is ratherconsidered to still be on the ring (similar to the manner in whichvirtual tributaries (VTs) are considered to not be terminated from thering). However, since each packet is addressed individually, squelchingis not needed as with a VT ring.

Combining the Non-BLSR Protected Layer 2/3 Channel and the Variable RateLayer 2/3 TDM Traffic Pipe

To describe the combining of a non-BLSR protected layer 2/3 channel anda variable rate layer 2/3 pipe on a single ring, a example from beforewill be expanded upon. In the previous example, it was assumed that aring supported OC-48 in each direction. In addition, since STS-24 wasallocated for the non-BLSR protected layer 2/3 channel in eachdirection, there was STS-12 left for each of the working and protectionchannels in each direction. From a layer 2/3 perspective, the hybridnetwork elements of the ring appear as packet network elements each withthe ability to transmit and receive the packet equivalent of STS-24 withthe other hybrid network elements. From a TDM perspective, the networkelements of the ring appear as a ring with STS-24 in each direction(STS-12 working and STS-12 protection).

To expand on this example, since from the TDM perspective the ring canbe viewed and is operated as an OC-24 BLSR, a variable rate layer 2/3pipe can be configured on this OC-24 BLSR. Thus, whereas in FIG. 7 c theentire ring bandwidth (e.g., OC-48 in each direction) was split betweenworking and protection channels and the variable rate layer 2/3 pipetook up part of both the working and protection channels when there wasno failure; in this embodiment half (OC-24 in each direction) of thephysical ring bandwidth (OC-48 in each direction) is allocated to formthe non-BLSR protected layer 2/3 channel and the other half is allocatedto form a BLSR (with working and protection channels) with a variablerate layer 2/3 pipe configured in that BLSR.

Configuring a non-BLSR protected layer 2/3 channel on an optical ring inconjunction with allocating a segment of the working channel andprotection channel for a variable rate layer 2/3 pipe increasesutilization of bandwidth of an optical ring, as well as the classes andtypes of services an owner of an optical ring can provide to customers.Hence, the owner of the optical ring extracts more use of the opticalring than with a standard BLSR.

FIGS. 9 a-9 b are conceptual diagrams of a 3 node bi-directional lineswitched ring (BLSR) having a variable rate layer 2/3 pipe and anon-BLSR protected layer 2/3 channel with exemplary traffic flowwhenever a failure exists and does not exist in the ring according toone embodiment of the invention. FIG. 9 a is a conceptual diagramillustrating exemplary traffic flow over an optical ring having avariable rate layer 2/3 pipe and a non-BLSR protected layer 2/3 channelwhile there is not a failure according to one embodiment of theinvention. Each node in a BLSR has an East and West span, but in FIG. 9a only the East and West transmit fibers 907, 911 of node 901 and theEast transmit fiber of node 903 are shown. The timeslots for each fiberare allocated to a working channel 921, a protection channel 919, and anon-BLSR protected layer 2/3 channel 917. The timeslots for the workingchannel 921 are divided between a working TDM pipe 913 and a workingchannel layer 2/3 subpipe 915 of the variable rate layer 2/3 pipe. Theremainder of the variable rate layer 2/3 pipe is allocated in theprotection channel 919.

A flow of TDM traffic 937 is transmitted in the working TDM pipe 913 ofthe working channel 921 of the East transmit fiber 911 from node 901 tonode 905. A flow of layer 2/3 TDM traffic 933 is transmitted in thenon-BLSR protected layer 2/3 channel 917 of the East transmit fiber 911from node 901 to node 905. A flow of TDM traffic having layer 2/3traffic as payload 931 is transmitted in the protection channel 919 andthe working channel 915 of the East transmit fiber 911.

In this illustration, all of the timeslots for the protection channel919 are being used as part of the variable rate layer 2/3 pipe. Inanother embodiment, only a subset of the timeslots allocated for theprotection channel 919 would be used as the variable rate layer 2/3pipe, thereby allowing the remaining timeslots of the protection channelto be used for other purposes such as another non-BLSR protected layer2/3 channel or extra traffic. Although the protection channel part andthe working channel part of the variable rate layer 2/3 pipe arenon-contiguous timeslots in FIG. 9 a, while there is not a failure inthe ring the 2 subpipes are used as the single logical pipe.

A flow of TDM traffic 923 is transmitted in the working TDM pipe 913 ofthe working channel 921 of the West transmit fiber 907 from node 901 tonode 903. A flow of layer 2/3 TDM traffic 927 is transmitted in thenon-BLSR protected layer 2/3 channel 917 of the West transmit fiber 907from node 901 to node 903. A flow of TDM traffic having layer 2/3traffic as payload 925 is transmitted in the variable rate layer 2/3pipe made up of part of the protection channel 919 and the workingchannel layer 2/3 subpipe 915 of the working channel 921 of the Westtransmit fiber 907.

The flow of the traffic 925 is destined for node 905 and thereforecontinues in the protection channel 919 and working channel layer 2/3subpipe 915 of node 903's East transmit fiber 909 to node 905. A flow ofworking TDM traffic 941 is transmitted from node 903 to node 905 in theworking TDM pipe 913 of the working channel 921 of node 903's Easttransmit fiber 909. A flow of layer 2/3 TDM traffic 945 is transmittedfrom node 903 to node 905 in the non-BLSR protected layer 2/3 channel917 of node 903's East transmit fiber 909.

FIG. 9 b is a diagram illustrating exemplary traffic flow over a opticalring having the variable rate layer 2/3 pipe and the non-BLSR protectedlayer 2/3 channel during a failure in the ring according to oneembodiment of the invention. In FIG. 9 b, the East transmit span 911 ofnode 901 has failed. The flow of working TDM traffic 923 and layer 2/3TDM traffic 927 continues to flow as illustrated in FIG. 9 a. Theworking TDM traffic 937 has been protection switched to flow over theprotecting TDM pipe 918 of the protection channel 919 on node 901's Westtransmit span 907 and node 903's East transmit span 909 untiltermination at node 905. Thus, part of the protection channel 919 on thespan 907 and 909 has been used. As such, the variable rate layer 2/3pipe carrying the traffic 925 has been reduced to only the workingchannel layer 2/3 subpipe 915 on the span 907 and 909.

The variable rate layer 2/3 pipe carrying the traffic 931 has beenreduced and switched to a protecting layer 2/3 subpipe 916 on theprotection channel 919 on the spans 907 and 909. The flow of working TDMtraffic 941 and flow of layer 2/3 TDM traffic 945 continue to flow asillustrated in FIG. 9 a.

With the combination of a non-BLSR protected layer 2/3 channel and avariable rate layer 2/3 pipe the traffic carried over an optical ring isdiversified. Moreover, a BLSR with a non-BLSR protected layer 2/3channel and a variable rate layer 2/3 pipe maintains a greater number oftraffic flows (luring a failure in the BLSR than a standard BLSR. Theprovider or owner of the optical ring can offer 4 types of services now.Firstly, the provider can provide typical guaranteed service for TDMtraffic. Secondly, the provider can provide the protection channel tocarry unguaranteed extra TDM traffic. Thirdly, the provider can providethe non-BLSR protected Layer 2/3 channel to carry Layer 2/3 TDM traffic.Fourthly, the provider can provide the variable rate layer 2/3 pipe tocarry layer 2/3 traffic at a guaranteed minimum bandwidth and a possiblemaximum bandwidth.

An owner of an optical ring can offer the optical ring as a variety ofnetwork packages to customers. An example of an optical ring with 100megabits per second (Mbps) transmit fibers having a variable rate layer2/3 pipe has previously been discussed. By adding a non-BLSR protectedlayer 2/3 channel to the 100 Mbps fiber, the network owner has a myriadof options. The network owner can divide the 100 Mbps of bandwidth asfollows: 30 Mbps of bandwidth allocated to a working channel; 30 Mbps ofbandwidth allocated to a protection channel; and 40 Mbps of bandwidthallocated to a non-BLSR protected layer 2/3 channel. In this example, 10Mbps of the working channel bandwidth is allocated to a working variablerate layer 2/3 pipe. The remaining 20 Mbps of the working channel is theworking TDM pipe The combination of the working variable rate layer 2/3pipe and the protection channel is the variable rate layer 2/3 pipe. Thevariable rate layer 2/3 pipe provides a maximum bandwidth of 40 Mbps anda guaranteed bandwidth of 10 Mbps.

The owner can provide the 20 Mbps working TDM pipe for typicalguaranteed TDM service. The owner can provide the 40 Mbps non-BLSRprotected layer 2/3 channel and the 40/10 Mbps variable rate layer 2/3pipe as a 60/30/10 hybrid variable rate pipe. Whenever a failure has notoccurred in the optical ring, TDM traffic is transmitted over a workingTDM pipe at 20 Mbps and layer 2/3 TDM traffic is transmitted over ahybrid variable rate pipe at 60 Mbps. When a failure occurs on a spancarrying the working TDM pipe and the hybrid variable rate pipe, the TDMtraffic is switched to a non-failing span and continues to betransmitted at 30 Mbps in the protection channel of the non-failingspan. The layer 2/3 TDM traffic traveling in the working variable ratelayer 2/3 pipe of the failing span is switched to a protecting variablerate layer 2/3 pipe in the non-failing span and is transmitted at 10Mbps. Layer 2/3 TDM traffic traveling in a hybrid variable rate pipe ina non-failing span loses 20 Mbps of bandwidth to the TDM trafficprotection switch from the failing span and 10 Mbps of bandwidth to theprotection switched layer 2/3 TDM traffic of the failing span. Thus, thelayer 2/3 TDM traffic traveling on the non-failing span is reduced from60 Mbps of bandwidth to 30 Mbps of bandwidth instead of 10 Mbps ofbandwidth.

If packet BLSR protection is implemented for the non-BLSR protectedlayer 2/3 channel, then the hybrid variable rate pipe offers differentrates of transfer in response to a failure on the ring. BLSR. Using thebandwidth division in the example already discussed traffic flows at thesame rates when a failure has not occurred on the ring. When a spanfails, the TDM traffic traveling in the working TDM pipe of the failingspan is protection switched and continues transmission at 20 Mbps. TheTDM traffic will also flow at the same rates as discussed in theprevious example whenever there is or is not a failure in the ring.Layer 2/3 TDM traffic traveling in the 10 Mbps working variable ratelayer 2/3 pipe of the failing span is switched to a 10 Mbps protectingvariable rate layer 2/3 pipe of a non-failing span. Layer 2/3 TDMtraffic traveling in the non-BLSR protected layer 2/3 channel of thefailing span is switched and tunneled through the non-BLSR protectedlayer 2/3 of the non-failing span. The layer 2/3 tunneled TDM traffic isstatistically multiplexed with the layer 2/3 TDM traffic already beingtransmitted in the non-BLSR protected layer 2/3 channel of thenon-failing span. The layer 2/3 TDM traffic traveling in the workingvariable rate layer 2/3 pipe of the non-failing span continues to betransmitted at 10 Mbps. Since the layer 2/3 TDM traffic of thenon-failing span and the layer 2/3 tunneled TDM traffic from the failingspan are statistically multiplexed, the owner can allocate the bandwidthof the non-BLSR protected layer 2/3 channel of the non-failing span isaccordance with network policy or priority level. Hence, the owner ofthe optical network still provides the hybrid variable rate pipe with aguaranteed bandwidth of 10 Mbps and a maximum bandwidth of 60 Mbps,however the owner can customize the bandwidth of the non-BLSR protectedlayer 2/3 channel.

If fragmented concatenation is implemented for the hybrid variable ratepipe, then traffic flowing over the hybrid variable rate pipe can bereceived and processed as a single concatenated set of traffic.Fragmented concatenation of the traffic flowing over the hybrid variablerate pipe will ease management and processing of the traffic flowing inthe hybrid variable rate pipe. In another embodiment, the hybridvariable rate pipe can include multiple non-BLSR protected layer 2/3channels. Fragmented concatenation can be applied to these multiplenon-BLSR protected layer 2/3 channel segments of the hybrid variablerate pipe in order to distinguish traffic from different customers.Distinguishing traffic from different customers enables the owner of thenetwork to offer varying classes of services and allocate the bandwidthof the hybrid variable rate pipe in accordance with policy decisions andthe classes of services offered by the owner of the network.

Exemplary Implementation of a Hybrid Network Element

FIG. 10 is a diagram of circuit components in a hybrid network elementaccording to one embodiment of the invention. While in this embodimentseparate switching mechanisms are provided for the TI)M and packetswitching (namely a TDM switch fabric and a packet mesh), alternativeembodiments could provide a single switching mechanism and/or differentswitching mechanisms (e.g., a packet switch fabric, a TDM mesh, etc.).In FIG. 10, four optical transmit fibers 1015, 1002, 1006, 1010 connectto physical ports 1011, 1014, 1018, and 1022 respectively. Four opticalreceive fibers 1017, 1004, 1008, and 1012 connect to physical ports1013, 1016, 1020, and 1023 respectively. TDM traffic is received overthe optical receive fibers 1017, 1004, 1008, 1012 and transmitted overthe optical transmit fibers 1011, 1014, 1018, 1022. The TDM traffic istransmitted and received as optical signals by physical connectioncircuitry (PCC) 1001, 1007, 1003, 1005. The PCCs convert optical signalsto electrical signals and vice versa for reception and transmission. TheTDM traffic is transmitted and received between the PCCs 1001, 1007,1003, 1005 and the TDM processing circuits (TPCs) 1019, 1031, 1025, and1037 respectively as electrical signals. The TPCs transmit and receiveTDM traffic from a control card (CC) 1009. In another embodiment of theinvention, each TPC and PCC is located on a single processing element,such as an application specific integrated circuit (ASIC). A hybridnetwork element is described in more detail in a patent applicationtitled “Method and Apparatus for Switching Data of Different Protocols”to David Stiles and Gerald W. Neufeld, filed on Mar. 30. 2001, Ser. No:09/823,480, Attorney Docket Number: 004906.P002, which is herebyincorporated by reference.

The layer 2/3 traffic can be switched through the CC 1009 or a packetmesh 1050. The TPCs are programmable to insert and extract particularSTSs that carry layer 2/3 traffic to be packet switched. If TDM trafficcontains layer 2/3 payload to be switched through the packet mesh 1050,then the TPCs 1019, 1031, 1025, and 1037 extract the layer 2/3 payloadtraffic from the TDM traffic and transmit the layer 2/3 traffic toingress layer 2/3 processing circuitry 1021, 1033, 1027, and 1039respectively. The TPCs 1019, 1031, 1025, and 1037 also receive layer 2/3traffic from egress layer 2/3 processing circuitry 1021, 1033, 1027, and1039 respectively. For a variable rate layer 2/3 traffic pipe, theegress layer 2/3 processing circuitry includes the ability to queue andstatistically multiplex layer 2/3 traffic before transmitting it to aTPC. The TPCs 1019, 1031, 1025, and 1037 process the layer 2/3 trafficplacing it into SONET/SDH frames for transmission in timeslots. The TPCs1019, 1031, 1025, and 1037 are programmable to insert and extractparticular STSs that carry the layer 2/3 traffic to be packet switched.

The CC 1009 detects failures, maintains a BLSR state machine, andupdates the TDM cross connect table in response to changes in the BLSRstate machine. The CC 1009 also sends a message to update the layer 2/3forwarding tables for the packet BLSR protection switching. In addition,the CC 1009 sends messages to reprogram the TPCs to handle a protectionswitch (e.g., reorient concatenations, redirect channels to packet meshand CC, etc.).

With respect to reprogramming the TPCs to handle a protection switch,assume that the network element illustrated in FIG. 10 is node 901 ofFIGS. 9 a and 9 b. Also assume that the ring in FIGS. 9 a and 9 b is a 2fiber OC-12 ring. The TPC 1025 of FIG. 10 is programmed to transmit TDMtraffic as a STS-1, STS-1, STS-1, STS-3 c, STS-3 c, and STS-3 c set ofpipes (the configuration depends on the version of non-BLSR protectedlayer 2/3 channel implemented, but this example is based on a versioncompliant with standard BLSR). When there is no failure in this example,the working TDM pipe 913 of the span 911 carries the working TDM traffic937 from node 901 to node 905 as STS-1 in channel 1. The span 911corresponds to the transmit fiber 1006 of FIG. 10. The traffic 931 iscarried on the span 911 from node 901 to node 905 in the working layer2/3 pipe 915 and the protection channel 919 as 2 pipes: the workinglayer 2/3 pipe 915 as 2 STS-1s in channels 2 and 3; and the protectinglayer 2/3 pipe as STS-3 c in channels 7-9, shown as 916 in FIG. 9 b.Traffic 933 is carried in the non-BLSR protected layer 2/3 channel 917as 2 STS-3 c pipes in channels 4-6 and 10-12. The TPC 1019 is programmedin the same manner.

While there is a failure in the span 911 carrying traffic from node 901to node 905, the cross connect table in the control card 1009 isupdated. Traffic to be transmitted out the PCC 1003 is now transmittedout the PCC 1001 and the TPC 1019 is reprogrammed. The non-BLSRprotected layer 2/3 channel remains unchanged. The traffic transmittedover the non-BLSR protected layer 2/3 channel continues to betransmitted in 2 STS-3 c pipes on channels 4-6 and 10-12 in thisexample. The working TDM traffic 923 is still transmitted as an STS-1over channel 1. The traffic transmitted in the working layer 2/3 pipe isstill transmitted as 2 STS-1s in channels 2 and 3. The TPC 1019 isreprogrammed to transmit the traffic 937 as an STS-1 in channel 7.Traffic is transmitted over the protecting layer 2/3 pipe 916 as 2STS-1s in channels 8 and 9. Node 901 informs node 903 of the failure.Node 903 reprograms a TPC which receives traffic from 901 and reprogramsa TPC which transmits traffic to node 905 in accordance with TPC 1019 ofnode 901. Node 905 is adjacent to the failure and has reprogrammed a TPCwhich receives and transmits traffic to node 903 in the same manner.

In contrast to the example provided, non-standard time slot allocationand non-standard concatenations enable flexible provisioning ofchannels.

In one embodiment, the fragmented concatenations are implemented byconstructing the hybrid network elements to include the ability to beprogrammed with which STSs are part of the fragmented concatenation. Inparticular, the TPC circuit is programmable to extract the STSs from theincoming SONET/SDH frames that make up the fragmented concatenation andprovide them to the IL2/3PC. The IL2/3PC will treat the incoming STSsthat are part of the fragmented concatenation as a single stream forstatistical multiplexing purposes. The egress of such traffic to thering will be handled in a similar manner.

In one embodiment, the non-BLSR protected Layer 2/3 channel(s) areimplemented by constructing the hybrid network elements to include theability to programmably mask BLSR protection on a STS-1 basis as definedin the standard defining the NUT channel.

In one embodiment, the non-BLSR protected layer 2/3 traffic can bepacket BLSR protection switched by constructing the hybrid networkelements to include the ability for the control card and the ingresslayer 2/3 processing circuitry to communicate to each other. In oneembodiment, the control card commands the ingress layer 2/3 processingcircuitry to update protection data structures in response to a changein the BLSR state machine. The ingress layer 2/3 processing circuitrymanages data structures indicating protection interfaces and/orprotection groups which are alternate physical interfaces or a tunnel.In another embodiment, the control card updates a data structure inresponse to a change in the BLSR state machine. The data structureidentifies a protection interface. The ingress layer 2/3 processingcircuitry maintains forwarding tables which reference the datastructure.

In one embodiment, combining the non-BLSR protected layer 2/3 channeland the variable rate layer 2/3 TDM traffic pipe is implemented byconstructing the hybrid network elements to inhibit BLSR protectionswitching on the timeslots allocated for the non-BLSR protected layer2/3 channel(s) and to communicate between the layer 2/3 section and TDMsection of the hybrid network elements. In particular, the control cardwill not alter the cross connect forwarding table for timeslotsallocated for the non-BLSR protected layer 2/3 channel. The egress layer2/3 processing circuitry will queue and statistically multiplex layer2/3 traffic before transmitting to the TPC.

Alternative Embodiments

The techniques shown in the figures can be implemented using code anddata stored and executed on computers. Such computers store andcommunicate (internally and with other computers over a network) codeand data using machine-readable media, such as magnetic disks; opticaldisks; random access memory; read only memory; flash memory devices;electrical, optical, acoustical or other form of propagated signals(e.g., carrier waves, infrared signals, digital signals, etc.); etc. Ofcourse, one or more parts of the invention may be implemented using anycombination of software, firmware, and/or hardware.

While the invention has been described in terms of several embodiments,those skilled in the art will recognize that the invention is notlimited to the embodiments described. The method and apparatus of theinvention can be practiced with modification and alteration within thespirit and scope of the appended claims. The description is thus to beregarded as illustrative instead of limiting on the invention.

1. A method comprising: providing a first communications service on anoptical ring of a first guaranteed bandwidth; and providing a secondcommunications service on the optical ring, the second communicationsservice having a maximum bandwidth, a second level bandwidth, and aguaranteed minimum bandwidth.
 2. The method of claim 1 wherein the firstcommunications service is telecommunications.
 3. The method of claim Iwherein the first communications service is data communications.
 4. Themethod of claim 1 wherein the second communications service is datacommunications.
 5. A machine-readable medium that provides instructions,which when executed by a set of processors, cause said set of processorsto perform operations comprising: provisioning a hybrid variable ratepipe on a span of an optical ring; and transmitting a set of traffic inthe hybrid variable rate pipe.
 6. The machine-readable medium of claim 5wherein the hybrid variable rate pipe transmits the set of traffic atmultiple transfer rates.
 7. The machine-readable medium of claim 5wherein the set of traffic is switched through a packet mesh.
 8. Themachine-readable medium of claim 5 wherein the hybrid variable rate pipecomprises: a non-BLSR protected layer 2/3 channel; a segment of theworking channel; and at least a segment of the protection channel. 9.The machine-readable medium of claim 5 wherein the hybrid variable ratepipe is allocated from a contiguous set of physical channels.
 10. Themachine-readable medium of claim 5 wherein the hybrid variable rate pipeis allocated from a non-contiguous set of physical channels.
 11. Themachine-readable medium of claim 5 wherein the hybrid variable rate pipeis allocated from a non-contiguous set of physical channels and the setof traffic is fractionally concatenated.
 12. The machine-readable mediumof claim 5 wherein the hybrid variable rate pipe has a first bandwidthon the span of the optical ring and a second hybrid variable rate pipehas a second bandwidth on a second span of the optical ring.
 13. Themachine-readable medium of claim 5 wherein the hybrid variable rate pipecomprises a non-BLSR protected layer 2/3 channel or the span, workingpipe on the span, and a protecting pipe on the span, the protecting pipeto protect a second working pipe on a second span of the optical ring.14. A machine-readable medium that provides instructions, which whenexecuted by a set of processors, cause said set of processors to performoperations comprising: transmitting a first set of traffic at a firstrate on a first span of an optical ring; transmitting a second set oftraffic at the first rate on a second span of the optical ring; reducingtransmission of the first set of traffic to a second rate while there isa failure on the second span; switching the second set of traffic to thefirst span; and transmitting the second set of traffic at a third ratewhile there is a failure on the second span.
 15. The machine-readablemedium of claim 14 wherein the first and second set of traffic aretransmitted in a non-BLSR protected layer 2/3 channel, a segment of aworking channel, and at least a segment of a protection channel.
 16. Themachine-readable medium of claim 14 wherein switching the second set oftraffic is performed with BLSR automatic protection switching.
 17. Themachine-readable medium of claim 14 wherein the first set of traffic istransmitted in a contiguous set of physical channels.
 18. Themachine-readable medium of claim 14 wherein the first set of traffic istransmitted in a non-contiguous set of physical channels.
 19. Themachine-readable medium of claim 14 wherein the first set of traffic istransmitted in a non-contiguous set of physical channels and the firstset of traffic is fractionally concatenated.
 20. A machine-readablemedium that provides instructions, which when executed by a set ofprocessors, cause said set of processors to perform operationscomprising: inhibiting automatic protection switching on a first channelover an optical ring; provisioning a working channel over the opticalring; provisioning a protecting channel over the optical ring;transmitting a set of traffic in the first channel, a part of theworking channel on a first span, and at least a part of the protectingchannel on the first span.
 21. The machine-readable medium of claim 20wherein the set of traffic includes layer 2/3 traffic to be switchedthrough a packet mesh.
 22. The machine-readable medium of claim 20wherein the first channel is a contiguous set of physical channels. 23.The machine-readable medium of claim 20 wherein the first channel is aset of non-contiguous physical channels and the set of traffic isfragmentally concatenated.
 24. The machine-readable medium of claim 20wherein the part of the working channel and the part of the protectingchannel are a contiguous set of physical channels.
 25. Themachine-readable medium of claim 20 wherein the part of the workingchannel and the part of the protecting channel are a set ofnon-contiguous physical channels and the set of traffic is fragmentallyconcatenated.
 26. The machine-readable medium of claim 20 wherein thepart of the protecting channel on the first span protects a secondworking channel on a se con d sp an.
 27. The machine-readable medium ofclaim 20 further comprising a part of a second working channel on asecond span and a part of a second protecting channel on the secondspan, the part of the second working channel and the part of the secondprotecting channel having a bandwidth different than the part of theworking channel and the part of the protecting channel.
 28. A networkelement comprising: a time division multiplexed (TDM) processingcircuitry to process a set of TDM traffic; and a control card coupled tothe TDM processing circuitry to provision and to manage a hybridvariable rate pipe, the hybrid variable rate pipe to carry the set ofTDM traffic.
 29. The network element of claim 28 wherein the controlcard to provision the hybrid variable rate pipe comprises masking BLSRprotection from a subpipe of the hybrid variable rate pipe.
 30. Thenetwork element of claim 28 wherein the control card to manage thehybrid variable rate pipe comprises: reprogramming the TDM processingcircuitry with a first set of concatenations for a first and secondsubpipe of the hybrid variable rate pipe while a failure does not exist;and reprogramming the TDM processing circuitry with a second set ofconcatenations for the first and second subpipe of the hybrid variablerate pipe while a failure exists.
 31. The network element of claim 28wherein the hybrid variable rate pipe comprises a non-BLSR protectedlayer 2/3 channel and a variable rate pipe allocated from a workingchannel and a protecting channel.
 32. The network element of claim 28wherein the hybrid variable rate pipe comprises a contiguous set ofphysical channels.
 33. The network element of claim 28 wherein thehybrid variable rate pipe comprises a non-contiguous set of physicalchannels.
 34. The network element of claim 28 further comprising: aningress layer 2/3 processing circuitry coupled to the TDM processingcircuitry, the ingress layer 2/3 processing circuitry to process a firstset of layer 2/3 traffic extracted from the set of TDM traffic by theTDM processing circuitry; and an egress layer 2/3 processing circuitrycoupled to the TDM processing circuitry, the egress layer 2/3 processingcircuitry to process a second set of layer 2/3 traffic and transmit thesecond set of layer 2/3 traffic to the TDM processing circuitry.
 35. Anapparatus comprising: a time division multiplexed (TDM) processingcircuitry to process a set of TDM traffic and extract a first set oflayer 2/3 traffic from the set of TDM traffic, the first set of layer2/3 traffic having been received on a set of physical channels; aningress layer 2/3 processing circuitry coupled to the TDM processingcircuitry, the ingress layer 2/3 processing circuitry to process thefirst set of layer 2/3 traffic; and an egress layer 2/3 processingcircuitry coupled to the TDM processing circuitry, the egress layer 2/3processing circuitry to process a second set of layer 2/3 traffic andtransmit the second set of layer 2/3 traffic to the TDM processingcircuitry; and a control card coupled to the TDM processing circuitry toinhibit automatic protection switching on a first subset of the set ofphysical channels and to protect a second subset of the set of physicalchannels with automatic protection switching.
 36. The apparatus of claim35 wherein the set of physical channels are contiguous.
 37. Theapparatus of claim 35 wherein the set of physical channels arenon-contiguous.
 38. The apparatus of claim 35 wherein the set ofphysical channels are non-contiguous and the first set of layer 2/3traffic is fragmentally concatenated.
 39. The apparatus of claim 35further comprising: a second egress layer 2/3 processing circuitrycoupled to the ingress layer 2/3 processing circuitry, the second egresslayer 2/3 processing circuitry to receive the first set of layer 2/3traffic and transmit the first set of layer 2/3 traffic; a second TDMprocessing circuitry coupled to the control card and the second egresslayer 2/3 processing circuitry, the second TDM processing circuitry toreceive the first set of layer 2/3 traffic from the second egress layer2/3 traffic and to transmit a second set of TDM traffic in a second setof physical channels, the second set of TDM traffic having the first setof layer 2/3 traffic; and the control card coupled to the second TDMprocessing circuitry, the control card to detect a failure on a pathcorresponding to the second TDM processing circuitry and switch thefirst set of layer 2/3 traffic traveling in a second subset and thirdsubset of the second set of physical channels to the third subset of thefirst set of physical channels, the second set of physical channelshaving at least three subsets of physical channels.
 40. A computerimplemented method comprising: provisioning a hybrid variable rate pipeon a span of an optical ring; and transmitting a set of traffic in thehybrid variable rate pipe.
 41. The computer implemented method of claim40 wherein the hybrid variable rate pipe transmits the set of traffic atmultiple transfer rates.
 42. The computer implemented method of claim 40wherein the set of traffic is switched through a packet mesh.
 43. Thecomputer implemented method of claim 40 wherein the hybrid variable ratepipe comprises: a non-BLSR protected layer 2/3 channel; a segment of theworking channel; and at least a segment of the protection channel. 44.The computer implemented method of claim 40 wherein the hybrid variablerate pipe is allocated from a contiguous set of physical channels. 45.The computer implemented method of claim 40 wherein the hybrid variablerate pipe is allocated from a non-contiguous set of physical channels.46. The computer implemented method of claim 40 wherein the hybridvariable rate pipe is allocated from a non-contiguous set of physicalchannels and the set of traffic is fractionally concatenated.
 47. Thecomputer implemented method of claim 40 wherein the hybrid variable ratepipe has a first bandwidth on the span of the optical ring and a secondhybrid variable rate pipe has a second bandwidth on a second span of theoptical ring.
 48. The computer implemented method of claim 40 whereinthe hybrid variable rate pipe comprises a non-BLSR protected layer 2/3channel on the s pan, working pipe on the span, and a protecting pipe onthe span, the protecting pipe to protect a second working pipe on asecond span of the optical ring.
 49. A computer implemented methodcomprising: transmitting a first set of traffic at a first rate on afirst span of an optical ring; transmitting a second set of traffic atthe first rate on a second span of the optical ring; reducingtransmission of the first set of traffic to a second rate while there isa failure on the second span; switching the second set of traffic to thefirst span; and transmitting the second set of traffic at a third ratewhile there is a failure on the second span.
 50. The computerimplemented method of claim 49 wherein the first and second set oftraffic are transmitted in a non-BLSR protected layer 2/3 channel, asegment of a working channel, and at least a segment of a protectionchannel.
 51. The computer implemented method of claim 49 whereinswitching the second set of traffic is performed with BLSR automaticprotection switching.
 52. The computer implemented method of claim 49wherein the first set of traffic is transmitted in a contiguous set ofphysical channels.
 53. The computer implemented method of claim 49wherein the first set of traffic is transmitted in a non-contiguous setof physical channels.
 54. The computer implemented method of claim 49wherein the first set of traffic is transmitted in a non-contiguous setof physical channels and the first set of traffic is fractionallyconcatenated.